A collection of useful scripts and prefabs for building VR titles in Unity 5.
Link: VRTK - Virtual Reality Toolkit
Archives: XR Developer tools
What is Unreal Engine 4
Unreal Engine 4 is a suite of integrated tools for game developers to design and build games simulations and visualizations.
Link: What is Unreal Engine 4
Zappar
An augmented reality platform and a creative studio, rolled into one Zappar’s in-house team of designers, developers, 3D artists and creative strategists have more experience of creating AR in the real-world than anyone in the known universe (as far as we know…).